Coupling arrangement



Jupe 22, 1948. wfw. MOE

` coUPLING ARRANGEMENT Filed Nov. 29, 1943l fill..

Inventor:

Patented June 22, 1948 UNITED STATES PATENT OFFICE coUPLING ARRANGEMENT William W. Moe, Stratford, Conn., assigner to General Electric Company, a corporation of New York Application November 29, 1943, Serial No. 512,173

My invention relates to electric transmission Vsystems and7 in particular, to an arrangement .for coupling different sections of such` a system.

An object of my invention is to provide an improved coupling arrangement for an electric transmission system.

Y Another object of my invention is to provide a nevi/"and improved means for coupling a cavity resonator to a concentric transmission line.

A further object of my invention `is to provide a new and improved arrangement for coupling a cavity resonator to a concentric transmission line `pling arrangement in which dielectric losses arer reduced to a minimum.

Still another object of my invention is to provide a new and improved arrangement for coupling a cavity resonator to an output circuit in which attenuation of unwanted frequencies is provided without attenuation of a desired frequency.

A still further object of my invention is to provide a new and improved coupling arrangement for the high frequency transmission system which is simple in construction, installation, and

adjustment.

One of the features of my invention is the use, in conjunction with a cavity resonator, of a stub transmission line short-circuited at one end and having an output circuit connected thereacross intermedi-ate the point of short-circuit and the point of -connection with the cavity resonator. lA centrally disposed conductor within the stub transmission line has a longitudinal bore in which is supported a metallic rod which extends beyond the end of the conductor into the cavity resonator. Means external of the stub transmission line are provided to adjust the position of the metallic rod within the cavity resonator to effect a desired transfer of electromagnetic energy between the resonator and the output circuit.

The features of my invention which I believe -to be novel are set forth with partieularity in the appended claims. My invention itself, however, both as to its organization and method o-f operation, together with further objects and advan- 2 Claims.

tages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing in which the single iigure illustrates a coupling arrangement constructed in accordance with my invention.

In the drawing, I have shown a space resonant cavity of the concentric or coaxial transmission line type and which comp-rises a tubular outer 4conductor I and a centrally disposed inner conductor 2. Means for exciting the space resonant cavity are provided and may take the form of an electric discharge devi-ce 3 having its anode Il coupled to the tubular outer conductor I and its grid yelectrode 5 connected to the inner conductor 2. The anode 4 and the grid 5 may :be mounted external tothe cavity resonator or these electrodes themselves may form a portion o-f the space resonant system defined in rpart by the conductors I and 2. The frequency of thecavity resonator defined by the conductors I and 2 may be adjusted in any well-known manner, for example, by means of a metallic plunger `(not shown) which engages the outer wall of" conductor 2 and the inner wall of conductor I and which is positionable along the longitudinal axis of these conductors.

The outer conductor I is provided with a circular aperture 1 landa stub transmission line 8 is mounted on the external surface of tubular outer conductor I concentrically With the aperture 1. The stub transmission line 8 comprises a tubular metallic outer conductor 9 and a centrally disposed inner conductor Il). Means for mounting the stub transmission line 8 on the external surface of conductor I comprises the bushing member I I which extends through the aperture 'I and has a flanged head portion I2 which engages the inner surface of conductor I. The bushing II is externally threaded and engages internal threads on the lower portion of tubular conductor 9. A washer I3 having a shape conforming to the outer surface of tubular conductor I is interposed between the lower end .of conductor 9 and tube I. The stub transmission line 3 at its upper end is short-circuited by means of a transverse metallic member M. In actual construction preferably `the members 9, Ill and I4 are formed as a unit. Connected across the stub transmission line at the point I6 between the short-circuit I4 and the opening l is an output circuit in the formv of a concentric transmission line having a tubular outer conductor Il and a centrally disposed inner conductor I8. The conductor I'l is connected to outer conductor 9 of the stub transmission line by means of a short sleeve I9 formed integrally with the outer conductor 9 and conducto-r I8 may be joined, as by soldering, to a conductor attached to inner conductor II] of the stub transmission line. The outer conductor I1 and the sleeve I9 may vbe externally threaded and held together by means .of a nut 2|.

Electromagnetic energy Lis :transferred ,between the .concentric transmission line I, 2l and the transmission line Il, I8 by means of a probe which extends into the space between conduct-ors I and 2. This probe or electrode is :constituted by a plate or disk 22, which is in spaced relation with the outer surface of inner `conductor-,2;` and attached to the lower endcf a conductive (rod-23 which passes through a longitudinal bore 25 in inner conductor Iii. The bore 25 in conductor Il] may be threaded, if desired, and the position of disk 22 with respect to conductor 2 maybe adjusted by means of a knurled knob 2e attached to theendfof rod 23.

...,In. the coupler arrangement described, the point of-connection i6 of the element Eil-to conductor lilrisselected so that the distance from vthe point I6 .to the short-circuit III is equal to a lquarter wave length or an odd multiple thereof ofthe ,electromagnetic wave-presentinthe resonant cav- .,ity comprising, conductors I and 2. With this construction, the stub transmission line 9A and I0 appearsas-ahigh impedance for currentsof the frequency ,of the electromagnetic wave to be ,transmitted so that .these currents travel over the conductor23tothe conductor 2li andthe concentrictransmission line I1, I8. For currents of otherufrequen'cies, the stub `transmission line 8 .-ibetween the points Iand I 4. offers less impedance so-that this quarter wave length section attenuates unwanted frequencies. `In eifect, therefore,

the .stub transmission line 8 functions as a fre- .,quency filter preventing passage of unwanted fre- Axlluencies and offering low attenuation to the `transmission of currents of ,desired frequency be- A,tween the cavity resonator and transmission line I'I,I8.

,In the. construction,moreover, Athe ratios of the ,diameters` of the various sections of concentric transmission line, such as the ratio of the diameters of. rod 23 and bushing II, 'of elements I9 ,and'ZiL and of conductors 9. and, I0, are made eqliattov each other and equal to the ratio of the vdiametersof `conductors Il and I8 and conductors j Land' 2 so that the path 'of the current flow' through rthe coupler is made to appear as a continuation ofthe external transmission line Il, I8 havingsthe same surge impedance as the output circuit.

By they construction described, it lis seen that jthe use of insulating materialsfor supporting conductors. and the .pick-up probe 22 is avoided and 'electrical dielectric losses are minimized. Fur- .thermoreV since adjustments of the couplermay bemade without removing external cables or even vmovingjthe stub line 8 or the `external line I1, I8, rigid and permanent connections of all ,these sections of lines may be employed and adjustments ot Vcoupling may Ibe eifected while the transmis- 'sion system is ,in operation.

"While I have illustrated a particular embodiment of my invention, it is apparent that ceri.tain,modi1cations may be made. Thus, instead of the .capacitive coupling constituted by the disk 122, anj inductive coupling inthe form of a loop connected between rod 23 and bushing Il may be employed. Similarly, while I have shown a particular type of cavity resonator, namely, the concentric transmission line I, 2, any other type of cavity resonator `or any means for transmitting electromagnetic energy may be employed, such as a dielectric wave guide of the hollowpipe type.

- It willv beV understood,@therefore 4that while I have shown a particular embodiment of my invenution, I do not wish to be limited thereto since many modcations may be made and I contem- Yplateby the appended claims to cover any such modifications `aswfall within the true spirit and vconcentric, line including an outer` conductorconnected at one end to theouter conductorof said transmissionline and surrounding said'opening,

said stub concentric lineV includinga central, conductor conductively connected ,to the ,outerl conductor of said stub transmissionlineatthe ,opposite end thereof, a `third concentric.transmission lline including inner and outer conductors .conductively -connected respectively with Atheinner and outer conductors of ,said stub transmissionline,

"the inner conductor of said stub transmissionline having an axial bore therein, `andan elongated conductor received vwithin said boreiand moi/Table with respect thereto and,terminatingdinamenlargementA positioned in spaced relation .with .respect to the inner conductor of `thej,first-mentioned transmission line.

4 2. Ahigh frequency system comprising aconcentric transmission line, including inner and outer cylindrical conductors, vthe outer .conductor `of said' linehaving anopening therein, .a vstub concentric line including an outer conductor connected at one end tothe outer conductor oisaid transmission line and surrounding saidppening, said stub concentric line includinga central conductor conductively connected to ,the outer conductor of said stub transmissionline atthe4 opposite end` thereof, a third concentrictransmission line including inner and outer conductorsconductively connected` respectively with .theinner and outer conductors of said stub transmission line at a quarter wavelength or odd multiple there- .,of from the point where the conductors of, said ,sion line.

WILLIAM=W."*MOE.

REFERENCESA .CITED The following references are of, record in the file of this patent:

UNITED STATES PATENTS Name Date Bowen Feb. 1; 1938 Number 

